A specialist in coal mine explosion prevention has called Solid Energy's decision not to re-enter the Pike River mine irrational.
Engineer David Creedy prepared a report, which concluded it would be safe to cautiously enter the mine to look for evidence of the cause the blasts which killed 29 men in November 2010.
The men's remains are still in the West Coast mine, behind a seal in atmosphere thought to be about 98 per cent methane.
Pike River owner Solid Energy is permanently sealing the mine, although its work was disrupted yesterday when a concrete firm stopped supplying cement due to protests by mine families.
Some want an attempt made to recover their men, and don't believe the mine is not safe to enter.
Creedy told the Herald "there wasn't a lot of logic" in Solid Energy's final decision not to re-enter the mine due to "potentially fatal risk factors."
Going into an area with a high level of methane was standard, he said, and rescuers would use breathing apparatus.
The risks that informed Solid Energy's decision included the possibility that fire related damage could cause collapse of the mine's roof, the maintenance of gas and ventilation in a difficult environment, the complexity of management of 600-plus risks associated with re-entry and the risk of entrapment due to a roof fall or vehicle fire.
But in the report, penned in 2014 by Creedy and former United Kingdom mines inspector Bob Stephenson on behalf of the Pike families, it is concluded that all risks could be "satisfactorily controlled."
The report requested that Solid Energy approve a cautious re-entry of the mine.
"We still stand by everything we said," Creedy told the Herald this week.
"We don't retract anything. We still believe we could get prepared and get the job done."
He called Solid Energy's risk assessment "excessive."
"If you followed it, it wouldn't be possible to build or enter any mine in the world.
"There were 600 risks and hazards identified. But they wouldn't all occur at the same time. If you get up in the morning and drive to your office, you probably face hundreds of hazards... It's when you cannot control a hazard that the risk becomes significant."
Creedy questioned whether Solid Energy's motivation to re-enter the mine was due to safety concerns, or financial or political pressure.
"Certainly there was no benefit for Solid Energy to go back in.
"They looked at the [coal] deposit and they assessed where the reserves they were interested in were, once they decided there was no reserve of interest then clearly there's no positive benefit for them to do anything," Creedy said.
"I wonder if they thought that coal was interesting in there, and potentially mineable, whether the outcome would've been different."
Solid Energy bought the Pike River mine in 2012, and entered into an agreement with the Crown committing them to undertake recovery of the men, provided it could be achieved safely, was technically feasible and financially credible.
In September 2013 Solid Energy announced a staged re-entry would begin.
In August 2014, WorkSafe chief mine inspector Tony Forster wrote to Solid Energy confirming his view that the re-entry plan was safe and technically feasible.
But in November 2014 the company announced it would not re-enter the mine, and relinquished its permit to extract coal from the area.
The company declined to speak to the Herald about the report this week.
But in a statement released on Monday, Solid Energy reiterated its stance on the decision.
"Our decision was based on an exhaustive investigation into the feasibility of safe re-entry and was backed by independent expertise," the statement read.
The company said the risk assessment process was rigorous and that their decision was informed by quality information regarding the residual risks.
Environment minister Nick Smith told the Herald a technical expert that would take a different view to anything could always be found.
But the "key view" was that held by the people with a legal responsibility for any decision to re-enter the mine - Solid Energy.
He said through the company, which is majority owned by the Government, more than $5 million had been spent on finding a safe way to re-enter.
"The Government is satisfied that the work done by Solid Energy was in good faith, was thorough and made every endeavour to try and get access," Smith said.
The Creedy and Stevenson report:
Authors Bob Stevenson and David Creedy are both experts in the coal mining field. Stephenson is a former deputy mine manager and HM Principal District Inspector of Mines in the United Kingdom, while Creedy has 30 years experience in coal mine methane, coalbed methane, institutional and energy projects.
The authors were unpaid. Their motivation was to ensure every reasonable effort was made to re-enter the mine and to recover the bodies.
Secondary objectives were to help establish the causes of the disaster and to disseminate the lessons learned to raise standards of safety, management and governance of coal mines globally to prevent such a disaster ever happening again.
Major hazards identified in a risk assessment prepared for Solid Energy could be eliminated or satisfactorily controlled to ensure they are reduced to as low as reasonably practicable using best industry practices.
Major issues raised in an October 2014 teleconference with Solid Energy senior management and their geotechnical advisor were:
(a) Management (b) Training (c) Six Hundred plus (600+) controls. (d) Failure of Rocksil Plug. (e) Integrity of Nitrogen Supply. (f) Use of Diesel Vehicles. (g) Ground Control. (h) Single Entry.
Solutions to each of these problems were laid out in the Creedy Stevenson report.
The authors found the "all encompassing" risk assessment could be broken down into more manageable pieces to affect better management, education, training controls etc.
The authors found that the project could proceed with greatly reduced risk to personnel by affecting re-ventilation of the drift to allow inspection.
Stevenson and Creedy said the initial inspection of the drift area should be limited from the portal (tunnel entrance) to the 1700 metre mark. "We agree that this section of the roadway is unlikely to have suffered damage."
Based upon the results of the inspection a decision can be taken on next steps.
"We request that the board of Solid Energy approve a cautious re- entry, subject to oversight by the chief executive, a detailed plan agreed by the rescue team and a no objection by WorkSafe NZ," Stevenson and Creedy concluded.